Fine Polycarbosilane Particles for Precursors of Silicon Carbide CeramicsSynthesized by Precipitation Processing in Solvents

摘要

Precursor-derived ceramics are fabricated by pyrolysis of preceramic polymers. Such precursorprocessing enables to design the structure on an atomic scale, which is attractive for synthesizingadvanced ceramic materials. On the other hand, various liquid processes to synthesize nano-sizedpolymer particles have been developed in fields of polymer technology. Such liquid processeswould be expected to be applied for polymer precursors of ceramics. In this study, chemicalprocessing to form fine polymer particles based on dissolution and precipitation in solvents wasinvestigated, in order to synthesize fine precursor powders for silicon carbide. The preceramicpolymer used in this study was a commercially available polycarbosilane. The solid polymer wasdissolved in n-hexane. Then, the polycarbosilane solution was mixed into ethanol which wasstirred with a magnetic stirrer. As the result, white precipitates were formed immediately in themixture. The precipitation is attributed to supersaturation by the sudden reduction in solubility ofthe polymer in each scattered droplet by the dilution with ethanol. The resulting precipitates weredried in a laboratory furnace. The scanning electron microscope observation showed that theobtained powder had very fine primary particle size of less than 100 nm, although these particleswere partially bonded. The dried powder can be converted to amorphous Si-C-O powder by thecure treatment and pyrolysis at 1000°C. β-SiC powder was obtained by the further heat treatmentat 1400°C due to the crystallization of the amorphous phase.